In recent years endovascular implantable devices have been developed for treatment of aortic aneurysms. These devices are delivered to the treatment site through the vascular system of the patient rather than by open surgery. The devices include a tubular shape of graft material such as woven Dacron, polyester polytetrafluoroethylene or the like to which is secured a tubular or cylindrical framework or scaffolding of one or more stents. The devices are initially reduced to a small diameter, placed into the leading or proximal end of a catheter delivery system whereafter the delivery system is inserted into the vascular system of the patient such as through a femoral incision. The leading end of the delivery system is maneuvered to the treatment site over a previously positioned guide wire.
Through manipulation of a control system that extends to the proximal end of the catheter from the distal end of the system outside the patient, the implantable device is deployed by holding the device at its location and withdrawing a surrounding sheath. The stent graft or implantable device can then be released and self expand or be expanded through the use of a balloon which is introduced with the stent graft introducible device. The stent graft becomes anchored into position to healthy wall tissue in the aorta (such as by barbs) whereafter the delivery system is removed leaving the device in position for reversing an aneurysm in the aorta. All blood flow is channeled through the stent graft so that no blood flow enters the aneurysm thereafter. As a result not only does the aneurysm no longer continue to grow and possibly rupture but the aneurysm actually begins to shrink and commonly disappears entirely.
For treatment of thoracic aortic aneurysms in particular it is necessary to introduce the implantable device high up in the aorta and in a region of the aorta which is curved and where there can be strong blood flow.
There has also been proposed the use of side arms in the thoracic arch region of the aorta to span between the implantable device and the great branch vessels of the thoracic arch to ensure flow to these vessels. If an implantable device which is essentially a tube is deployed in the thoracic arch without side branches then loss of blood flow to these great branch vessels could cause serious consequences to a patient.
The great vessels are essentially on the outer side of the curve of the thoracic arch. The delivery device for the implantable device, being formed from a resilient material, when extended up into the thoracic arch will essentially form the largest diameter curve it can and hence it will lie in the aorta on the side of the greatest arch. The delivery device will therefore lie close to the great vessels and there will be little or no working space to catheterize the branch vessels from the implantable device or to catheterize fenestrations in the implantable device from the branch vessels. Slight misalignment between the fenestrations in the implantable device and the branch vessels could cause significant problems in catheterization.
It is desirable therefore that a deployment device or deployment system is provided in which the proximal end of the device, the end in the thoracic arch, takes up a lesser diameter of curvature so that some working space is provided on the outer side of the curve of the thoracic arch during the introduction process.
It is the object of this invention to provide a device which will overcome at least some of these problems or at least provide the physician with a useful alternative.
Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis means the end of the aorta, deployment device or prosthesis further away in the direction of blood flow away from the heart and the term proximal means the portion of the aorta, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels similar terms such as caudal and cranial should be understood.
Throughout this discussion the term “stent graft” is intended to mean a device which has a tubular body of biocompatible graft material and at least one stent fastened to the tubular body to define a lumen through the stent graft. The stent graft may be bifurcated and have fenestrations, side arms or the like. Other arrangements of stent grafts are also within the scope of the invention.